Of the eight teams that have strolled or struggled into the quarter-finals of the World Cup, five will have an extra spring in their step this week. The bounce has nothing to do with anything that happened in the final round of pool matches, although Wales and Ireland have every reason to be more than satisfied with their victories against Fiji and Italy respectively.

No, it's to do with a little word that began to circulate from the All Blacks' training ground on Saturday. Dan Carter was injured. It had to be a ruse, one of those tricks thought up by the old copper and now assistant coach of New Zealand, Steve Hansen, whose mind can go down some marvellously devious pathways.

But then came the photo of Carter writhing on the ground. Still, it might just be part of the cunning plan. A page went up on the web, Carter out of World Cup, only to be withdrawn. Finally, on Sunday morning came the prosaic confirmation that Carter had torn a tendon in his groin during kicking practice and was out of the tournament.

Now, there is an obligation to view this objectively, as a great shame for the sport. But it should also be reported that the thought of facing the All Blacks minus Carter is infinitely more attractive than the prospect of spending the next three weeks trying to work out a way to stop the best No10 on the planet.

He presumably hurt himself "kicking in" the balls that were to be used in the match against Canada, which only goes to confirm just how dangerous this activity is. It did for Jonny Wilkinson's minders, Dave Alred and Paul Stridgeon, and now it has done for Carter.

Rugby union is complicated enough anyway, without having a whole new protocol attached to the pre‑match routine of softening up a Gilbert's dimples. How about the referee handing the team that are about to kick-off a ball hitherto unseen? An unknown ball, a ball still on its factory settings.

And while we are on the subject of this ever more confusing game, wouldn't it be a vaguely good idea if the referees chose to blow for infractions of some of the more obvious laws, like the forward pass? Ever since some boffin propounded that it was possible for a player on the move to deliver a "momentum" pass – one that looked forward but wasn't – one of the fundamental tenets of the game has become subject to some non-binding agreement. You don't have to be Isaac Newton to see that there are some iffy passes being given.

Jonny's England are not part of the group with a spring in their step. Another day for England, another reason to tread more lugubriously across New Zealand. Just when he was briefed yesterday to fend off questions about the Dunedin Three, Martin Johnson had to gen up on the latest instalment of the saga of Mike Tindall in Queenstown.

And then he found out that Delon Armitage, a rare beacon, was being cited for his challenge on Chris Paterson in the Scotland game. Carter is the last person on the England manager's mind.

Fortunately, they play France in the quarter-final. Marc Lièvremont's team make England look positively overflowing with good cheer. France, with defeats against New Zealand and Tonga, have not so much sailed into the quarters as drifted in at the speed of seaweed. England might slip on it, but so heavy is their tread that it should be just another crunch of kelp, and on they trudge.

South Africa will play Australia in Wellington on Sunday. Australia have swung between defeat in their second game to Ireland and recovery against the USA and Russia. Their only constant has been an injury list longer than most, Drew Mitchell being their latest casualty.

There has been a similar sense of lurching in the South Africa camp, with uncomfortably narrow victories against Wales and Samoa around reassuringly and more typically brutal defeats of Fiji and Namibia. The Springboks will miss Frans Steyn at No12, because he brought a burly creativity and a whopping boot to the midfield.

South Africa and Australia have both won the World Cup twice. Their meeting, thanks to Ireland winning Pool C, should be the pick of the quarter-finals. The last time they played at the World Cup was a classic at Twickenham in 1999, a semi‑final decided by a drop goal from about two miles by Stephen Larkham. It might come to that again: Quade Cooper against Morne Steyn. I trust both will have kicked in their balls adequately.

Wales will play Ireland. Take your pick. Brian O'Driscoll said after Ireland's second‑half surge against Italy that the quarter-final will be determined only on the day itself, but it seems to be an Irish belief that they have the measure of Wales.

There again, Wales believe they have hit new levels of fitness. Please, as I say, take your pick: Sam Warburton against Sean O'Brien.

And New Zealand will play – and beat – Argentina. They have no Dan Carter, but the Pumas have also lost their talisman, the No8 Juan Martín Fernández Lobbe. The All Blacks have too many attacking options in too many positions to be troubled for long. They have one more round before they really have to start worrying, as only New Zealand can, at the World Cup.